As a method for producing a toner, which contains a color former compound, a color developing agent, and optionally a color erasing agent and is capable of erasing an image formed on a recording medium by erasing the color, a melt-kneading method is usually adopted. The melt-kneading method is a method for producing desired toner particles by melt-kneading a binder resin, a color former compound, a color developing agent, a release agent such as a wax, a charge control agent, and the like, cooling the resulting kneaded material, finely pulverizing the cooled material, and then, classifying the resulting fine particles.
However, in the case of producing the toner particles by a melt-kneading method, kneading is performed at a high temperature of, for example, about 200° C., and therefore, the color former compound and the color developing agent are uniformly dispersed in the binder resin. Since the color is developed by reacting the color former compound with the color developing agent, if the color former compound and the color developing agent are uniformly dispersed, the color developing property is decreased.
Further, in the case of producing the toner particles by a melt-kneading method, when a binder resin or the like has a color erasing action, the color is erased during kneading, and therefore, it is necessary to select a material which does not have a color erasing action as a binder resin to be used in the production. Accordingly, a binder resin having excellent fixability sometimes could not be used in the production of a toner.
Further, although the reduction in the particle diameter of a toner is demanded for achieving a high-quality image, there is a limit to the reduction in the particle diameter by a melt-kneading method.